


Kustard Week

by LazySintastic13 (EmeraldWriter)



Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell (Undertale), M/M, Multiple AUs used, Underfell Sans (Undertale), kustard - Freeform, was just having fun
Language: English
Status: Completed
Published: 2018-10-09
Updated: 2018-10-08
Packaged: 2019-07-28 10:39:10
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings, Graphic Depictions Of Violence
Chapters: 7
Words: 3,574
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/16239935
Author URL: https://archiveofourown.org/users/EmeraldWriter/pseuds/LazySintastic13
Summary: Using Angst Dialogue Prompts, these stories were born. And no, I'm not following the norm. :)





	1. This will be the last time you lie to me

**Author's Note:**

> Kustard Week happened on tumblr, and now posting it here on Ao3 XD

**Summary for the Chapter:**

> Rated M

He had to admit, it had been in a long time since he came to a room like this. Cold and bland. They really need to redecorate in here. At least make the stone walls a different colour, paint over the natural.

He thought yellow would look nice … but then thought otherwise since it reminded him of piss. Brown was shit, and orange might be too bright. It doesn’t deserve purple, blue is depressing, black is a hole, red might make people angry, and white is a mental hospital.

Huh.

Maybe gray was the right colour after all.

It was a practical room too. A desk, a lamp, and two chair, one of which he currently occupied with his own ass.

Speaking of the other person who’s going to occupy the other seat, the door opened to reveal said person.

“Hey, sweetheart.” He waved, the chains rattled with it.

‘Sweetheart’ sat on the other chair without saying a word.

Ah, grumpy as always. Maybe he was the cause, maybe not. Who knows, he wasn’t a mind reader.

And they could sit there, do a staring contest and all that jazz, but the silence irked him.

“So,” he drummed his fingers on the desk, the clacks had rhythm. He might be a musician. “Am I going to—”

“Sans Fontaine.”

“Oh, the full name?”

“I had your records checked.” Sans snorted at the statement. “I bet those cuffs on you is practically an old friend.”

“Something like that.” Sans gazed blankly at the red eye lights that narrowed into pinpricks, and picked up on the low and deep throaty rumble.

“Listen, I don’t give a fuck what you’ve been up to, but this will be the  _last_ time you lie to me! One more time, Sans, and I’ll stop bailing your stupid ass, and you can get your free ticket to rot in fucking Alcatraz for all I care.” He slammed his fist on the table, creating a small crater that made Sans look at the cracks in appreciation. “Are we clear,  _Sweetheart?”_

Ooh. Sans’ soul trembled in anticipation. Sounds like he got himself a ticket for a hot and angry fuck when they get home. He wondered if he could keep the handcuffs then.

Sans grinned with nonchalance, darkly chuckling as he looked at the other monster with a predatory gaze. It caused the one across him to shudder, and growled even more fiercely at him. It would’ve been intimidating but the coloured cheeks made it lose all merit.

“You better have those forms already signed, because I don’t think I could wait.”

“Y-You—”

“5 seconds.” Sans leaned back on his seat. “And I’m porting us both out.”

Red’s eye lights widened, hesitating for a moment.

“Got 4 seconds, love.”

The skeleton cursed, and hastily ported out, making Sans’ deep laugh resound in the room.

The sex was going to be worth it.


	2. This isn’t going to be fixed. You’ve ruined this for good now

**Summary for the Chapter:**

> General Fluff

What lay before them was an abomination. Of a creature that wouldn’t even dare to label as their kind, but a  _creature_ nonetheless.

It was a ghastly viscous goo of black, having a face of a bowling bowl. The wind that it sucked, came out as a low howl, as if it was one of those zombie movies, groaning for food and brains; stuck in perpetual hunger.

It gave an eerie vibe all around, as it  _moved_ like a slug.

The two skeletons watched it try to make its way to a spoon on the counter.

“… Red.”

“Shut up. I know.”

“This isn’t going to be fixed.”

“I mean, maybe I could—”

“It’s what caused  _this_ to be  _born.”_ Sans sighed in exasperation, the back of his skull beaded in cold sweat when he gazed at the …  _thing_ again. “You’ve ruined this for good now.”

Red deflated, unable to argue any longer. He couldn’t help but feel wronged in his heart as he grumbled. “Told you I don’t cook.”

“… You only had to boil eggs!” Sans pointed at the still moving blackness of destruction. “How did you manage to make this?”

“Uh. Magic?” Red sweated profusely out of nervous habit, twiddling his thumbs and looking at anywhere but Sans.  

Sans looked at his husband with a wry smile, before summoning a blaster and aiming it at the abomination.

“Wait Sans! Our kit—”

The explosion shook the ground, and there was now a gaping hole to where their kitchen was.

“—chen …”

The two stood there in silence, looking through their new backyard entrance … It was a nice and sunny out.

“You want to just eat out?” Red offered, looking to Sans who met his gaze … and shrugged.

“Sounds good.”


	3. When did you think you could hurt me again? Today? Tomorrow?

**Summary for the Chapter:**

> Rated T

_Had it been that easy? Did you think I was so easy?_  Red’s fists tightened at his sides, fiercely glaring at Sans who he had punched in the face. The other’s cheek began to swell.

“When did you think you could hurt me again?” Red gritted his teeth, growling lowly. His eye lights narrowed into pinpricks. “Today?!” His body shook at the surging rage filling his core. “Tomorrow?!”

Sans didn’t say a word, staring blankly back at Red. It only incited the other’s ire.

But suddenly, the fuel in him ran out—his anger evaporating into thin air.

Receiving silence as his answer, Red let out a small laugh that grew and transformed into a hysterical one; it came off as desperate as his tears slid down his sockets.

And then, Red stopped. He returned Sans’ expressionless gaze with his own. “I’m done.”

Red’s soul ached, twinging in pain when he saw that even then, it still didn’t garner any reaction from Sans.

Where was the man he loved? The one who promised him happiness?

 _Nowhere,_  Red thought. Disheartened, and broken, he steeled himself to turn around and take a step away from Sans. To just get away from it all.

But he still couldn’t help but wonder what happened for it to come to this. Red wished he knew the answer. But he sure was hell never ever going to get anything from Sans.

Sans watched Red’s figure until the latter was completely out of sight. Only then, did he shed a tear of his own, and whispered to no one:

“I’m sorry …” It was for the best.

* * *

_“CUT!”_

The word had Sans slump his shoulders, and breathed out a sigh. “Finally. Music to my ears.”

Red came walking back to Sans when the latter left the set, handing him his coffee and kissing his cheek. “You did great hun.”

“Heh, I should be saying that to you. Your performance packed a  _punch.”_

Red snorted at the pun, nudging his spouse’s shoulder playfully. “And yours was a  _tear-jerker.”_

“Pfftt. Dude, I almost spat my coffee. Can’t a man get some peace and drink his drug?”

They got scolded by the director when Red howled with laughter for distracting others. So the two skeletons were sent back to their dressing rooms, and were told to get ready for the next scene.

Damn. No rest for the stars. It was really tough being in showbiz.


	4. How could you think this wouldn’t hurt me?

**Summary for the Chapter:**

> Rated T

The metallic taste made his brows furrow tight as it spilled from his mouth and dripped down his jaw. He couldn’t stop the cough that was wrenched from his throat, sputtering the blood and saliva on the floor. No longer could he hold himself up, so he let the weight of his body slide him down the wall to the ground.

His chest heaved, breathing with difficulty as he gazed upon the very monster he had once trusted his life with. And rather than the pain—the torture being done to him, it was nothing compared to the betrayal he was facing.

“H-How could you t-think this w-wouldn’t hurt me?” He managed to say, but even then, it practically took everything in him to do so. It hurt to speak.

But the answer he received stabbed his soul.

“Because you never really cared in the first place.”

The dagger twisted deep.

How could his best friend, his partner, his  _everything_ think that he never cared at all? When all that he’d done, it was all for him; for his sake.

He didn’t understand. Not a single bit.

And his confusion must’ve been evident, for the latter laughed monotonously. “You’re probably wondering what I’m talking about right? Seeing as you haven’t done anything to hurt me, and yet I betrayed you.”

The skeleton came forward to crouch in front of his sorry figure. There was no sympathy in the blank eye lights that stared back at him. Just agony.

“But you betrayed me once. And again, and again. No matter what I did, the outcome was the same. So this time,” Sans grabbed Red’s chin hard, making the latter wince from the pressure. “I’m going to betray you, before you do it again.”

Red was slammed back, his vision doubling and becoming blearily from the tears that pricked in his sockets.

“How does it feel? Not good right?” Sans stood up. “I know. I know all too well.”

Red couldn’t utter a sound. He didn’t have the energy to even keep his consciousness from slipping. The edges of his sight darkening, as Sans’ figure became hazier by the minute, until he could no longer fight it and succumbed to the darkness.

* * *

“Ain’t that a twist! Ahahaha! You were actually betrayed this time! Ahahahaha!”

Red stayed quiet, ignoring the laughing demon. His focus was only on Sans that reflected on a gigantic crystal ball.

Seeing that the demon was being ignored, he huffed indignantly and hovered by the skeleton’s side. “Have to say, it took your lover more than a thousand times before he had enough of your shi—”

“I won the bet.” Red simply stated.

The demon snorted, his little tail whipped back and forth in agitation of the reminder. “I know!”

“Your promise.”

“I said I know! Hmph! I was just about to do it okay? But don’t forget that this means you still belong to me! You’re still my pawn!”

“… I know.” But with this, everything would revert back to the way it was supposed to be.

Back before the ‘Incident’ happened. Before the world fell to shit. Before Papyrus died.

And … before he even met Sans.

Everything will be reseted, but this time without the harrowing future in store.

And this time, without Red.

As it was supposed to be.


	5. You’re never going to be the same after this

**Summary for the Chapter:**

> General Fluff - Rated T

Red watched with cold sweat as Sans nursed the glass in his hands, swirling the purple concoction. And honestly, he was kind of apprehensive of what it may do to his mate.

“You sure ‘bout this?”

“Uh.”

Yes, what a comforting response. Thanks Sans. It made Red huff, inciting a nervous laugh from the latter.

“Well, you know, better now than never.”

“Riiighht. You know you’re never going to be the same after this.”

“Yup. That’s the point.” Sans looked back down on the … less than appetizing liquid. “Going be worth it though.” He muttered under his breath, and without preamble, steeled his soul to gulp it all down.

Red’s breath hitched as he watched in anticipation and trepidation.

And when Sans finished all the contents, they both waited with bated breath.

Suddenly, Sans’ body began to glow, and the skeleton hunched his body, groaning as he clutched his chest.

Red wanted to so badly rushed to him, but he knew that he can’t. Instead, he could only form fists at his sides to hold himself, keep himself in check, and watched.

It was with horror and awe in seeing bones enlarged, the breaking ticks made him wince as it also expanded. Soon, Sans was growing new appendages, still growing and  _growing_.

Red had to move back a good few metres, watching his mate shine brighter that it blinded him.

Only when Red felt hot air blow on his arms that shielded his face did the skeleton lowered his arms and opened his eyes to see.

He blinked, and Sans blinked back at him before expelling air from his  _snout_.

“W-Woah! Holy shit Sans! You’re gorgeous!” Red couldn’t help but exclaim as he marvelled at the white dragon before him, admiring the gleaming almost pearlesque scales and the curled sharp-tipped horns. It really accentuated those deep blue slitted eyes. He went as far as to pet Sans’ large face, and even nuzzling to it with glee. “Hehe, it’s much more menacing than my own beast form. You’re so lucky being a dragon.”

Sans curled himself around his mate, his long tail moved to play with Red, making the latter giggle. “So cool, sweetheart. Wish I was a dragon too. Then we can even fly together!” Red’s shoulders slumped at the reminder of what he was.

Chipmunk. A fucking  _chipmunk_. Chipmunk! What good would that do? He wasn’t menacing, or even powerful! Really made one feel wronged. The world was so unfair.

Sensing Red beating himself up over his beast form, Sans curled his tail to lift his mate and placed him on his head.

“W-Woah.” Getting the hint, Red latched onto the horns for leverage, and he gasped with glee. “A-Are we going to fly?” The question came out as a whisper, but as if answering him anyway, Sans spread his wings wide, and began to flap them, pushing them off the ground.

“Holy shii _iiitttt!”_  Sans suddenly blasted up to the sky, and Red almost lost his grip from the velocity. He did; however, floated and dropped on Sans’ head when the latter paused, deeming that they were high enough in the sky, and proceeded to leisurely fly about thereafter.

Though he couldn’t showcase his expressions without looking scary, Sans’ soul felt as if it grew wings of its own and soared when he heard the awe and happiness from his mate.  

“Oh stars, this is incredible. Look Sans! There’s our village. Oh, over there is the Meruka Caves. And there is the Cavern of Beginnings! Sans look, look!” Red kept pointing here and there, like a small child discovering new things. The sight really warms the heart.

Seeing this, Sans knew that it was worth it. The reward  _definitely_ outweighed the risk.


	6. Are we going to carry on like this or are you going to give him back to me

**Summary for the Chapter:**

> Rated M for the violence

He wiped the metal with the smooth fabric, a useless action in the attempt to clean and add shine to it because it already was. Still, he performed the act with nonchalance, seated with his back leaned on the cushion of his red leather chesterfield chair.

The time continued to tick, evident from the noise of the wall clock above his fireplace.

When he felt content with his work, he grasped the grip and turned the object to inspect the other side, before lowering it to his lap.

Only then, did he glance at the monster on the floor; legs and arms behind the other’s back, both bound tightly.

His eyes roamed at the wounds and bruises, making for a sorry and pitiful figure. It didn’t make him feel anything but disgust that the man was ruining his carpet. It was a good thing blood was easy to clean. Otherwise, he’d burn the monster along with his carpet.

“So,” his deep voice caused the pitiful man to shudder with fear. “Are we going to carry on like this?” There was a click, before the constant ticking as the cylinder was spun.

“Or are you going to give him back to me.”

The monster trembled under his narrowed gaze, and another click resounded in the room as the cylinder shifted back to its original place.

“If you piss on my carpet too, I’m shooting your stomach.” He said with ease, returning to wiping the other side of the metal.

“P-Please. M-Mercy.” The monster sputtered. “I-I-I didn’t know. I—”

_Click._

The man cowered, voice caught in his throat as the barrel was aimed at him.

“Listen,” He really wanted a cigar right now. The idiot was grating his nerves. “You tell me what I want to hear, and I won’t kill you. Ain’t it easy?”

“B-But I don—”

_Bang._

A scream was wrenched out of the monster, the blood pooling and getting absorbed by the carpet. His poor poor carpet. Oh, now the man was crying too.

“Must hurt like a bitch to have your arm shot huh.” He clicked the hammer, shifting to the next bullet. “Gonna shoot the other one too if you lie one more time, buddy.”

Ah, now it led to incoherent sobbing. He really wasn’t going to get anywhere with this—

Just then, his phone rang. It made him raise a brow at the unknown caller before answering it.

“Hel—”

_“S-Sans.”_

The voice was weak and low, but it caught the skeleton’s attention nonetheless. He gripped the phone tight. “Are you safe right now, sweetheart?”

_“Y-Yeah. I t-think … Sans?”_

“Yeah?”

_“I’m … ‘m f-fucking scared.”_

Sans’ soul tightened. It was rare for Red to admit such a thing, and it spurred him to get his lover back as soon as possible. More so when he heard the faint hiccupping and sniffling.

“It’ll be all right, Red. I want you to stay strong for me just a bit more, can you do that, love?”

_“O-Okay. Yeah. Hic. I-I can.”_

The shakiness of Red’s voice did nothing to quell Sans’ worry, but since Red managed to call him, he was now able to trace and locate his lover.

Sans stood from his chair, and aimed the muzzle at the weeping monster’s head. He didn’t need him anymore. Sweetly, he said to Red, “I’ll be with you in 10 minutes, sweetheart.”

_“C-Can you also s-stay in the l-line?”_

Sans smiled warmly, “Of course.”

_Bang._

Really, his poor carpet. But now, getting his lover back was top priority. So Sans adorned his fedora and jacket, and left the room. He’ll let the cleaners handle the mess.

**Notes for the Chapter:**

> My favourite XD


	7. You don’t own me, I don’t belong to you

**Summary for the Chapter:**

> Rated T

He sneered as he picked up a large urn, stars that’s heavy, and wobbly tossed it at the smug monster that was supposed to be his master. It missed, obviously, but damn it!

“You don’t own me!” He pointed shakily—he  _wasn’t_ shaking! “I don’t belong to you!”

Fuck the man in front of him and—Did he just grin wider?! Oh hell no! What was so amusing you punk?

The guy even had the  _nerve_ to laugh. Laugh!

“You’re so cute when you’re angry sweetheart.”

“I’m not your sweetheart! You—”

“Now, now,” The monster ported behind Red, startling a squeak as his arms wrapped around the other’s waist. “No need to get your panties in a twist, Red.”

Red’s eye twitched, and was about to go on another rant when he suddenly felt the atmosphere become heavy. He found himself quaking as fear wracked his nerves.

“I spent good money on you, so while I’m pretty lenient most of the time, I also expect you to  _behave.”_

Red could only find himself nodding frantically, now knowing that his owner wasn’t a monster he should be picking a bone with.

Abruptly, the heavy tension left, causing Red to sag into the other’s embrace. It made the monster chuckle, much to his dismay, but he much preferred this than that threat.

“See, wasn’t that hard right?”

Red yelped as his owner now carried and laid him on the bed. Going as far to even tuck him in. This master of his was confusing the hell out of him.

“Sorry for scaring you there buddy. Was actually just teasing you. I like it when you’re feisty. It’s really cute.”

The comment made Red huff before pouting right after. He  _wasn’t_ cute! Hmph. Well, at the very least, he should know that guy’s name or something. So he asked, “What’s your name?”

His master smiled, and it looked cuter than the smug one. “Sans.”

“Maste—”

“Just Sans is fine.”

Red nodded. “Right. So Sans,”

“Hmm?”

“What the heck did you even buy me for?” Straight to the point, but Red needed to know since, apparently, he  _did_  belong to Sans. It aggravated him a little—a lot —just thinking about it. He felt an oncoming and unwanted headache.

Answering the question, Sans stated with ease. “To be my bride.”

“… What?”  _What?_

“Yup.”

Red stared at Sans who only kept smiling at him. “You’re joking right?”

“Nah, I’m pretty serious about it.”

“Wait.”  _Hold on. Time out. Who’s a bride?_

“You’re my bride.”

Did he say that out lou—not the point!

“I can’t be your bride?!”

Sans titled his head. “Why?”

Red sputtered incredulously. “We don’t even know each other?!”

“And isn’t it nice that we’ll have the rest of our lives to do that?”

“… You’re insane aren’t you.”

“And you’re rude as fuck.”

This guy. Just from first impression, Red could tell that Sans had power, and money. Not to mention that the skeleton was also really handsome, carried charm, and hella strong magically and physically, if the threatening performance was anything to go by. The monster seemed very protective—maybe possessive too. 

… Well. Damn. 

Red didn’t see much downside into actually marrying Sans. As a slave with nothing, but himself, he was the only one actually benefiting from this. And if that’s the case …

“Fine. I’ll marry your stupid ass.”

Sans snorted. “Glad to hear it.”

“… You’re really weird for choosing someone like me to marry.” Red yawned, the coziness of the bed was making him drift off.

He didn’t manage to hear Sans’ words as the latter watched him with fondness. 

“Heh, even if you didn’t remember saving me, I’m just glad that I finally have you by my side.”


End file.
